# Leetcode 2544: Alternating Digit Sum Solution

Here, we will see how to solve Alternating Digit Sum Solution of leet code 2544 problem.

You are given a positive integerÂ `n`. Each digit ofÂ `n`Â has a sign according to the following rules:

• TheÂ most significant digitÂ is assigned aÂ positiveÂ sign.
• Each other digit has an opposite sign to its adjacent digits.

You have to returnÂ the sum of all digits with their corresponding sign.

Example 1:

```Input: num = 123
Output: 2
Explanation: (+1) + (-2) + (+3) = 2```

Example 2:

```Input: num = 886996
Output: 0
Explanation: (+8) + (-8) + (+6) + (-9) + (+9) + (-6) = 0.```

## Alternating Digit Sum Solution in C++:

Here, we will be solving problem in multiple ways with code.

C++ code 1:

```class Solution {
public:
int alternateDigitSum(int n) {

int k = 1, ans = 0;

while(n>0)
{
ans += (n%10) * k;
n = n / 10;
k *= -1;
}

return -k * ans;
}
};```

C++ code 2:

```class Solution {
public:
int alternateDigitSum(int n) {
int total_digit = 0, tmp = n, sign, sum = 0;

while(tmp) {
total_digit += 1;
tmp /= 10;
}
if (total_digit % 2 == 1) {
sign = 1;
} else {
sign = -1;
}
while(n) {
sum += (n % 10) * sign;
n /= 10;
sign *= -1;
}
return sum;
}
};```

Output:

```Input: n = 111
Output: 1
Explanation: (+1) + (-1) + (+1) = 1.```

Time complexity: O(n)

Space complexity: O(1)

To check more leetcode problem’s solution. Pls click given below link:

https://www.techieindoor.com/category/leetcode/

https://www.techieindoor.com/category/interview-questions/

Posted in C++, Easy, Leetcode